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38 Cards in this Set

The dust is composed of ices, oxides, carbon and heavier elements such as iron.
The gas is almost entirely hydrogen, which makes up 75% of mass in the universe.

What does the solar nebula hypothesis propose?

That planets were formed from the disk of gas and dust that surrounded the sun as it formed.

What are the steps in solar system formation?

1. slow spinning cloud of gas and dust within the milky way galaxy.
2. Nebular cloud begins to collapse. Centrifugla forces cause the cloud to collpase to a central plane which eventually becomes the plane of the solar system.
3. As cloud collpases, gravity supplies the energy to heat up and compress the center. Proto sun is formed.
4. Revolving masses of gas and dust become trapped in stable orbits around protosun.
5. Increasing heat and pressure creates nuclear fusion as hydrogen fuses into helium releasing energy and stopping the contraction. Protosun becomes true sun.
6. Within circulating rings, matter cools and starts to condense into larger particles.
7. Constant collisions cause boulders to coalesce undergravity and become smaller bodies of matter called planetesimals.
8. Planetesimals grow into protoplanets, and eventually true planets.

What are meteorites?

Chunks of rock or metal that fall to the earth from space. They are remnants of the primordial solar nebula.

What are planets, moons, and space debris?

Form as by product of star formation from nebulas. They are leftovers that didn't get incoroporated into the central star which accumulated >99% of the mass.

How does the growth of true planets occur?

By differentiation of materials according to density, under the influence of internal heating.

What happens during differentiation?

Denser material accumulates in the core while lighter material moves to the outer area.

What happened during Earth's differentiation?

Heavy materials like iron collpased towards the center while lighter materials such as oxygen and silicon moved to the outher surface.

What does differentation result in?

Most planets having an interior dense core, surrounding less dense mantle, and a thin least dense crust.

As planets grow, where does the heat come from?

Frictional heating through constant collision
Accumulation of radioactive elemetns that release heat as they decay.

When did the entire differentiaon process on earth probalby finish?

Around 4 billion years ago.

Where did Earth's origional atmosphere come from?

Derived by volcanism and widespread outgassing.

What was the origional atmosphere like?

Rich in carbon dioxide and water vapor as well as other reactive gasses.

Where did our oceans come from?

At some point, all of the water vapor in the atmosphere began to condense and fall as rain, thus creating our oceans.

What is the earth composed of?

An interior core, a thick mantle and a thin, outer crust.

Where does the Earth derive its composition?

Constant addition of material from the solar nebula by collisions early in its hisotry.

What happens to pressure with increasing Earth depth?

Increases due to the weight of the overlying rock.

What happens to temperature as you move to the center of the Earth?

Increases.

The rate of change in temperature w/ depth is called..

Geothermal gradient.

The inner core is solid/liquid?
The outer core is solid/liquid?

Inner core: solid
Outer core: liquid

What is the solid inner core like?

Almost pure crystalline iron almost as surface of the sun but frozen at the center of the planet by intense pressure.

What is the liquid outer core?

A dense sea of molten iron w/ traces of other metals.

What generates the Earth's magentic field?

The flow of liquid iron in the outer core.

What is the mantle composed of?

silicate rock and metal oxides that is a solid that acts like a very thick liquid. Behaves like plastic.

What is the crust like?

relatively thin and has the lowerst density. Composed of mostly silicate rock that acts as a brittle material.

What is seismology?

using earthquake waves to see inside the earth.

What are earthquakes?

Abrupt release of energy stored along faults in the Earth by the build up of stress along the fault.

Why do earthquakes occur?

When enough energy accumulates to exceed the frictional strength of the rocks on either side of the fault plane, the rocks shift abrputly, sending out seismic waves that hit the surface, causing ground shaking characteristics.

What are the two types of body waves?

P waves: primary/pressure wave
s waves: secondary wave or shear wave

What are P waves?

first wave to arrive because they travel fastest through the Earth.
Travels through solid rock and liquid material.

What are S waves?

secondary wave or shear wave
-slower than p waves (arrive at seismograph later)
shears rock sideways or up and down at right angles to direction of travel
-only travels through solids.

What are the paths taken by seismic waves?

They are not straight, nor is the speed constant. May reflect off of sharp boundaries or may refract upon contanct with a layer of different density within the earth.

What is the speed of a wave dependent on?

dpends on the density of the rock through which they travel. Velocity increases w/ density

When does density and velocity of seismic waves typically increase?

at the boundaries between each of the compositional layers in the Earth (crust/mantle boundary).

Where do p wave velocities decrease?

From the mantle to lquid outer core

Another abrupt increase in P wave velocity occurs..

at the outer to inner core transition.

How do we know the core is mostly composed of iron?

Iron meteorites were likely originally derived from planetesimals that had differentiated into a core, mantle and crust.
We also know that the seismic velocity of compressed iron is consitent w/ P wave velocities through Earth's core.